Recently, applications and traffic related to IP (Internet Protocol) have increased, and a high affinity with IP has been requested for mobile communication networks. The trend to introduce IP techniques into mobile communication networks is called the ALL IP trend, which is a subject discussed by various standardization organizations. For example, 3GPP2 (3rd Generation Partnership Project 2) is discussing phased developments relative to the ALL IP trend for a cdma 2000 network (3GPP2 S.P0038-0 Version 1.1.8 Draft, Sep. 17, 2003 (non-patent document 1)).
As broadband access of the Internet has spread, the use of multimedia communication, such as data communication, VoIP and animation email, has come to be widely employed. The quality of a transfer delay, a transfer delay fluctuation, an information error, etc., that is required for multimedia communication varies, depending on the individual media. And the need that quality of service (QoS) be appropriately controlled for individual media has increased.
As a general QoS control method for the Internet, there is Diffserv, which has been standardized by IETF. According to Diffserv, a TOS (Type of Service) field is re-defined in an IP header, and a packet forwarding operation is performed by using the value of a DSCP (Diffserv Code Point) in the TOS field. A packet forwarding operation designated using a DSCP is called a PHB (Per-Hop Behavior).
There are roughly three Diffserv classes: EF (Expedited Forwarding) is the highest priority class, AF (Assured Forwarding) is the intermediate class, and Default is the best effort class. AF is divided into four other classes, in accordance with priority levels of transmission, and each of these classes is divided into three more levels, in accordance with priority levels for packet abandonment. Using Diffserve, packet transfer control is performed based on a DSCP, which is control information included in a packet. This is a scalable method based on a network scale (a number of relay nodes), and is widespread.
QoS control is also discussed for a mobile communication network.
For example, a study of QoS control for a fourth generation mobile communication system is reported in NTT DoCoMo Technical Journal Vol. 5, No. 2, pp. 41-46, September 2003 (non-patent document 2).
The cited reference discloses an architecture wherein control is performed by mapping, to a QoS class at an IP lower rank, an IP packet that belongs, for example, to the EF or AF class, or a characteristic use where QoS for the IP layer is linked to QoS for wireless. However, for a radio transfer, commonly, an IP packet is divided or a radio transfer packet is formed on a RAN (Radio Access Network) or at a radio base station, and generally, a one-to-one correspondence is not established between an IP packet and a packet at a lower IP layer. In the cited reference, QoS control performed when an information unit differs for each layer, because of the division of a packet, is not specifically disclosed.
Further, for 3GPP2, for example, performance of QoS control between end points, an MS (Mobile station) and a CN (Correspondent Node), has been discussed (3GPP2 S.P0079-0 Version 0.0 5.5, Jun. 11, 2003 (non-patent document 3)). A typical system configuration for 3GPP2 is shown in FIG. 1. Reference numeral 8 or 340 denotes an MS (Mobile station), and 7 denotes a CN (Correspondent Node). Further, reference numeral 1 denotes an IP network; 2 and 6, border routers; 3, a node device PDSN (Packet Data Service Node); 4, a packet control device BSC/PCF (Base Station Controller/Packet Control Function); 5, an AP (Access Point); and 9, a RAN (Radio Access Network). When QoS control for an IP layer is to be performed between end points, it is requested by the PDSN and the MS that a service provided by a layer lower than the IP should have high affinity relative to a service provided by an IP layer.
An explanation will be given for example conventional IP packet transfer control performed on a 3GPP2 mobile communication network. Assume that, for a network shown in FIG. 1, an IP packet is transmitted from BR 2 to PDSN 3. An example for the transmission of information from PDSN 3 to MS 8 is shown in FIG. 2. An IP packet 10 received by PDSN 3 is mapped into different connections 11 and 12, in accordance, for example, with a QoS class indicated in control information for a header, and is transmitted to PCF 4. The connections 11 and 12 from PDSN 3 to PCF 4 are connections for an A10 interface, and the PDSN prepares an A10 packet based on the IP packet and transmits the A10 packet to the PCF. Connections 13 and 14 from the PCF 4 to an AP 5 are connections for an A8 interface, and the PCF 4 prepares an A8 packet based on the A10 packet, and transmits the A8 packet to the AP 5. A scheduler 115 for the AP 5 controls the transmission of the received A8 packet to a wireless medium, in accordance with a priority level consonant with the connection 13 or 14.
For example, suppose that the connection 14 is the Best effort class and the connection 13 is the high priority class. The scheduler 115 provides transmission control for the A8 packet to the connection 13 prior to the A8 packet to the connection 14. When RLP (radio Link Protocol) is employed, the AP 5 generates RLP packets 15 and 16 from the A8 packet, in accordance with the RLP, and transmits to a wireless medium a signal generated at an RLP lower layer. The MS 8 includes: an AT (Access Terminal) 18, which has a radio transmission/reception function; and a TE (Terminal) 19, which executes an application. The AT 18 demodulates information based on received signals 15 and 16, reconfigures an IP packet 17 and transmits it to the TE 19. The network configuration in FIG. 1 is merely an example, and PDSN 3 and PCF 4, for example, may be mounted in a single case. Further, BSC and PCF, for example, may be mounted in different cases. A10 and A8 are protocols employed for communication between the PDSN and the PCF and between the PCF and the AP.
An example format for the A10 packet prepared by the PDSN 3 is shown in FIG. 3. Assume that the PDSN 3 receives an IP packet 20. When PPP (Point to Point Protocol) is employed by the PDSN 3 and the MS 8, the PDSN 3 configures a PPP packet 21 by adding PPP control information to the packet 20. Further, the PDSN 3 forms a frame 22 by adding control information 7E to the PPP packet in accordance with a framing protocol that is employed based on the PPP. The PDSN 3 divides the frame 22 into maximum transfer units (MTUs) 26 and 30. As control information, IP headers 24 and 28 and GRE (Generic Routing Encapsulation) headers 25 and 29 are respectively added to the obtained data 26 and 30 to form A10 packets 23 and 27. The PDSN 3 transmits the A10 packets 23 and 27 to the PCF 4.
An example format for the A8 packet prepared by the PCF 4 is shown in FIG. 4. Assume that the PCF 4 receives the A10 packet 23. The PCF 4 divides data 26 into data 35 and data 36, in accordance with an information transfer unit such as ECB, created by the AP 5. In this case, the ECB (Error Control Block) is an RS (Reed Solomon) coding unit for error control. As control information, the PCF 4 adds IP headers 38 and 42 and GRE headers 39 and 43, respectively, to the obtained data 35 and 36, and forms A8 packets 37 and 41. The PCF 4 transmits the A8 packets 37 and 41 to the AP 5.
An example format for an ECB that is prepared as a radio transmission unit by the AP 5 is shown in FIG. 5. Assume that the AP 5 receives the A8 packet 37. In accordance with control information included in the GRE header 37, the AP 5 stores the data 35 in an ECB 55. The scheduler 115 of the AP 5 employs a priority level consonant with the A8 packet 37 for storage of the data 35 in the ECB 55. The priority level is determined by employing a DSCP included in an IP header. The AP 5 calculates an error correction parity 57, by employing the stored information, and stores it in the ECB 55.
Another example format for a radio transmission unit prepared by the AP 5 is shown in FIG. 6. Assume that the AP 5 receives the A8 packet 37. The scheduler 115 of the AP 5 employs a priority level consonant with the A8 packet 37 for the formation of an RLP packet from the A8 packet 37. The AP 5 prepares an RLP packet 120 by adding an RLP header to the data 35 of the A8 packet 37. The AP 5 adds control information (Stream Layer Header) to the RLP packet 120, and creates a stream layer packet 121. The AP 5 adds control information (Session Layer Header) to the stream layer packet 121, and prepares a session layer packet 122. The AP 5 adds control information (Connection Layer Header) to the session layer packet 122, and creates a connection layer packet 123. The AP 5 adds, to the connection layer packet 123, control information (Encryption Protocol Header/Trailer, Authentication Protocol Header/Trailer and Security Protocol Header/Trailer), and prepares a security layer packet 125. The AP 5 adds control information (MAC layer Trailer) to the security layer packet 125, creates a MAC layer packet 126, and transmits it.
In “Transport QoS in the Radio Access Network (RAN)”, A20-20020107-016, (January, 2002), a written contribution by 3GPP2 (non-patent document 4), performance of the QoS control for the RAN using Diffserv is disclosed. According to the disclosure of the cited reference, for IP capsulation, the PDSN maps the DSCP of an IP header to be capsulated into the DSCP of an IP header (outer IP header) to be obtained by capsulation. For example, while referring to FIG. 3, the PDSN 3 copies the DSCP of the IP header 50 for the IP packet 20 to the IP headers 24 and 28 of the A10 packet. Further, in FIG. 3, for example, the PDSN 3 adds, to the IP headers 28 and 28 of the A10 packet, the DSCP that is consonant with the DSCP of the IP header 50 of the IP packet 20. And the PCF 4 prepares the A8 packet based on the received A10 packet. At this time, the PCF 4 copies, unchanged, the DSCP of the outer IP header of the A10 packet to the DSCP of the outer IP header of the A8 packet.
In “A PROPORTIONALLY FAIR SCHEDULING ALGORITHM WITH QOS AND PRIORITY IN 1XEV-DO”, Kuenyoung Kim, Hoon Kim and Youngnam Han, Proceedings PIMRC2002, Lisbon, September, 2002, p. 2239 (non-patent document 5), a scheduling algorithm for an AP in conventional 1xEvDO is disclosed. According to this reference, the AP performs scheduling by using an algorithm called proportional fairness. Proportional fairness is an algorithm by which the throughput of a system is increased to the maximum and transmission periods are fairly allocated to mobile stations. An overview will now be explained. Mobile stations measure C/Is, and request from an AP the highest transmission rates that can be determined to be attained. At this time, the C/I is a ratio of signal power to interference power. The mobile stations request from the AP transmission rates for each period of time, called a slot. Assume that the transmission rate requested by the mobile station is a DRC. The AP calculates an average value R for the transmission rates actually allocated to the mobile stations, and further, calculates DRC/R. The AP allocates a transmission period to the mobile station for which the DRC/R is the maximum.
Example scheduling performed by the system in FIG. 1 is shown in FIG. 28. In FIG. 28, the horizontal axis represents time, and the vertical axis represents a DRC/R value. The DCR/R values for the MS 8 and the MS 340 fluctuate, depending on changes in the transmission environment. During a period 601, the DRC/R of the MS 8 is greater than the DRC/R of the MS 340. The AP 5 allocates the period 601 as a period for a transmission to the MS 8. During a period 602, the DRC/R of the MS 340 is greater than the DRC/R of the MS 8. The AP 5 allocates the period 602 as a period for a transmission to the MS 340. During a period 603, the DRC/R of the MS 8 is greater than the DRC/R of the MS 340. The AP 5 allocates the period 603 as a period for a transmission to the MS 8. During a period 604, the DRC/R of the MS 340 is greater than the DRC/R of the MS 8. The AP 5 allocates the period 604 as a period for a transmission to the MS 340. In non-patent document 5, an example wherein weighting is performed using k and scheduling is performed using a value of k*(DRC/R) is disclosed. It is mentioned that k is obtained as a result of a delay or a data rate; however, a specific method is not disclosed.